The present invention relates to compositions and methods for treating, reducing, ameliorating, or preventing infections caused by antibacterial drug-resistant bacteria. In particular, the present invention relates to such compositions comprising quinolone carboxylic acids or derivatives thereof, and methods of using the same. More particularly, the present invention relates to such compositions comprising fluoroquinolone carboxylic acids or derivatives thereof, and methods of using the same.
Bacterial pathogens continue to pose a serious threat to public health as indicated by a worldwide resurgence of bacterial diseases. In some instances, common infections, such as otitis and sinusitis, have become difficult to treat because of increasing bacterial resistance to antibiotics. Such resistance may be attributed to prior widespread, and largely effective, therapeutic and prophylactic use of antibiotics, which, unfortunately, over time has also selected for resistant strains of various bacterial pathogens. Of particular concern to the public health have been the emergence and proliferation of bacterial strains that are resistant to multiple antibiotics in the current arsenal of antimicrobial agents. Such multiantibiotic-resistant (“MAR”) bacterial strains include species of Gram-positive bacteria, such as, antibiotic-resistant strains of Staphylococcus aureus, Enterococcus fecalis, and Enterococcus fecium, which, along with antibiotic-resistant Gram-negative strains of Escherichia coli, constitute the most frequent etiological agents of nosocomial (hospital-acquired) diseases, such as septicemia, endocarditis, and infections of wounds and the urinary tract. S. aureus is currently the most frequent cause of nosocomial bacteremia and skin or wound infection. Streptococcus pneumonia, another Gram-positive bacterium, causes several serious and life-threatening diseases, including a contagious meningitis, bacteremia, and otitis media. Annual mortality from S. pneumoniae infection alone is estimated at between 3-5 million persons globally. More recently, clinical accounts of highly aggressive skin and tissue infections by “flesh-eating” strains of Group-A streptococcus bacteria, such as Streptococcus pyogenes, has heightened the concern and need for new or improved antibacterial agents.
B-lactam antibacterial agents, which comprise four major groups: penicillins, cephalosporins, monobactams, and carbapenems, and work by inhibiting the bacterial cell wall synthesis and thus cell division, are the most common treatment for bacterial infections. However, due to their widespread use, bacterial resistance to these drugs has increased.
As a response to bacterial resistance to β-lactam drugs, other antibacterial agents have been developed that target different components of the bacterial cells. For examples, aminoglycosides, macrolides, tetracyclines, and amphenicols inhibit different aspects of bacterial protein synthesis. Antibacterial glycopeptides (such as vancomycin and cycloserine) inhibit the synthesis of peptidoglycan, a major structural component of Gram-positive bacteria cell walls. Quinolones interfere with cell division by targeting bacterial DNA transcription/replication through inhibition of their DNA gyrase and/or topoisomerase IV. Sulfonamides and diaminopyrimidines interfere with the bacteria's ability to synthesize folic acid, thus inhibiting their ability to synthesize the necessary nucleosides thymine and uridine. J. N. Samaha-Kfoury et al., Br. Med. J., Vol. 327, 1209 (2003).
As new antibacterial drugs are applied, the process of natural selection continues to work in favor of the bacteria strains that have mutated to acquire a tolerance of these new drugs. Nowhere has this issue been of greater concern than with the Gram-positive bacteria pneumococci, enterococci, and staphylococci. Staphylococcus aureus is perhaps the pathogen of greatest concern because of its intrinsic virulence, its ability to cause a diverse array of life-threatening infections, and its capacity to adapt to different environmental conditions. The mortality of S. aureus bacteremia remains approximately 20-40% despite the availability of effective antimicrobials. S. aureus is now the leading overall cause of nocosomial infections and, as more patients are treated outside the hospital setting, is an increasing concern in the community. F. D. Lowy, J. Clin. Invest., Vol. 111, No. 9, 1265 (2003).
Therefore, there is a continued need to develop novel antibacterial agents and improved pharmaceutical compositions that are effective against bacteria that are resistant to some of the common prior-art antibacterial drugs. It is also very desirable to provide novel and more effective compositions and methods for the treatment, reduction, amelioration, or prevention of infections caused by a bacterium that is resistant to at least a prior-art antibacterial drug. In addition, it is also very desirable to provide novel and more effective compositions and methods for the treatment, reduction, amelioration, or prevention of infections caused by some of the Gram-positive bacteria that are resistant to at least an antibacterial drug.